idct2 This function computes the inverse 2-D discrete cosine transform of input matrix. Y = idct2(X) Y = idct2(X, M, N) Y = idct2(X, [M, N]) X: Matrix or integer M, N: If specified Matrix X is padded with M rows and N columns. This function computes the inverse 2-D discrete cosine transform of matrix X. If M and N are specified, the input is either padded or truncated to have M rows and N columns.